Magnetic crossbar switch



y 1963 s. L. HJERTSTRAND 3,099,727

MAGNETIC OROSSBAR SWITCH Filed Jan. 22, 1962 I nventor 5. HJE RT STRAND Attorney United States Patent 3,099,727 MAGNETIC CROSSBAR SWITCH Svante Lennart Hjertstrand, Hagersten, Sweden, assignor to International Standard Electric Corporation New Yorlr, N.Y., a corporation of Delaware Filed Jan. 22, 1962, Ser. No. 167,506 Claims priority, application Sweden Feb. 1, 1961 8 Claims. (Cl. 200-87) This invention relates in general to crossbar switches and in particular to crossbar switches in which each contact set is selectively operable in response to the establish ment of a magnetic attraction between the intersecting horizontal and vertical rows of contact multiples. Its principal object is to provide a new and improved crossbar switch of the above character which is simple yet reliable in operation.

Crossbar switches requiring a plurality of hold magnets and select magnets are gradually being replaced by electronic devices such as gas-gap tubes, transistors, and PNPN diodes, primarily as a result of expense and size requirement of conventional crossbar switches. While these electronic devices have advantages in switching speeds, they are subject to disadvantages regarding their reliability, economy, maintenance and transmission quality. While the disadvantage of electronic components as to economy and reliability may be overcome, the transmission qualities are not expected to match those of precious metal pressure type contacts. One reason for this is that the amount of crosstalk or attenuation depends on the contact resistance and the degree of isolation of one contact from another. Electronic circuitry can compensate for the noted attenuation by amplification but such amplification will increase the level of crosstalk and thus rendering electronic components unsuitable for many uses.

According to the present invention, the foregoing disadvantages are overcome by providing an economical, compact crossbar switch using precious metal contacts which are easily actuated with a minimum of travel.

A feature concerned with the compactness of the inventive device resides in the elimination of the usual hold and select magnets and associated hold and select bars.

Another feature resides in the arrangement wherein the contacts are operated by magnetic attraction therebetween at each contact staokup without a separate energizing coil per stackup being required.

Other objects and features of the invention will become apparent and the invention will be best understood by reference to the accompanying drawing comprising FIG- URES l to 3 wherein:

FIGURE -1 shows two sets of contacts together with a portion of the well-known intersecting horizontal and vertical contact multiples modified according to the invention;

FIGURE 2 shows one embodiment of the invention wherein the contact sets have contact points carried by an insulating member secured to one of the contact multiples; and

FIGURE 3 shows another embodiment where the contact points are carried by separate horizontal and vertical multiples.

Referring now to FIGURE 1 of the drawings, a description of the invention will be given.

The switch section illustrated comprises a horizontal contact multiple strip 1 and a pair of vertical contact multiple strips 2 and 11. These multiple strips are made of a flexible magnetic material which has good electrical conductivity. The multiple strips are arranged in horizontal and vertical rows with the horizontal and vertical rows being located in adjacent parallel planes.

A pair of contact plugs of magnetic and electrical characteristics, such as 3 and 4, are mounted on contact multiple strip 2 and extend into close but non abutting relation with the multiple strip 1. Contact plugs 9 and 10, shown in more detail in FIGURE 3, are mounted on contact multiple strips 1 and 1x1 in similar relation but they are not both secured to the same strips, These contact plugs serve as contact points when the intersecting multiple strips are actuated.

Operating conductors 5, 6 and 12. are associated with their respective multiple strips 1, .2 and 11 and are positioned between the noted contact plugs. Thus, each contact multiple strip has its own operating conductor suitably securedthereto. The operating conductors may be secured to their associated multiple strips in any suitable manner which permits the conductors to be electrically insulated from the multiple strips.

In order to operate any contact set of the crossbar switch, simultaneous and cooperating currents are placed on the operating conductors associated with the horizontal and vertical contact strips which define the contact set to be operated. The noted currents sufficiently magnetize the operating conductors to cause their attraction toward one another thereby bringing the two intersecting multiple strips into electrical conductivity with each other through the associated contact plugs.

The current flowing through the selected operating condoctors is regulated so that electrical contact is established at a crosspoint only both operating conductors are energized. Thus, a contact set will not be operated if only one operating conductor is energized. In this way it is possible to select a connection between any horizontal and any vertical contact multiple by energizing the corresponding operating conductors.

Any contact set operated may be retained in its operated condition when the energizing current is removed from the operating conductors by the remanence in the magnetic circuit. This magnetic circuit is composed of the two contact plugs and the portion of each multiple strip lying between the plugs.

An operated contact set may be released by energizing either of the multiple strip with a current in the opposite direction from the operating current. As is well known, the release current may be of substantially smaller magnitude than the operating current.

In order to achieve as good contact properties and contact pressure as possible, the contact surfaces are covered with precious metal, such as gold or rhodium in a thin layer. In order to secure separation between the movable parts of a contact on releasing, the whole system may be closed in oil or in any other liquid with insulating properties and suitable surface tension.

By this method the movable parts in an operated contact are subjected to a separating force, which is counteracted by the remanence. On releasing, the separating force becomes efiective when the remanence force is eleminated by the described counteracting current in either of the selection conductors belonging to the contact in question.

For selection applications some contacts can co-operate so that poles belonging to the same device in a system operate simultaneously in a manner familiar, for example, in crossbar systems. In such cases the selecting circuits containing the selecting conductors such as 5 and 6 are connected in series or in parallel in order to achieve operation simultaneously. Thus, the contact system can function as a selecting device and a registering device in telecommunication systems. The operation of the selector equipment is effected by currents in the selector conductors, which are connected to one or more markers controlling the system, :and which by numerical and nonnumerical selections and by methods whose principles are known, investigate the possible devices in the selector system which would be useful in the actual case.

FIGURE 2 shows a contact plug mounting arrangement wherein each of the plugs 3 and 4 are mounted on an insulating strip 7 with neither of the contact plugs in electrical contact with the associated contact multiple strips 1 and 5. When the multiple strips are attracted to each other, the contact plugs establish electrical contact therebetween.

FIGURE 3 shows the contact plugs 9 and 10 electrically mounted on associated multiple strips. Plug 9 is electrically connected to strip 11 and plug 10' is electrically connected to strip 1. The contact assembly can be constructed according to any of these arrangements.

While the principles of the invention have been described above in connection with specific apparatus and applications, it is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention.

I claim:

1. A cross bar switch contact assembly comprising a plurality of flexible contact strips of magnetic material arranged in parallel rows in first and second parallel planes with the contact strips in one plane positioned normal to the strips in the other of said plane, contact means positioned between the contact strips of said planes at each of the crossover points of the contact strips of one plane with the contact strips of the other plane, each of said contact means and adjacent portions of said contact strips defining a separate magnetic circuit, and a selectively energiz-able operating conductor extending longitudinally of each of said contact strips for generating magnetic flux in the associated contact strip, the generation of magnetic flux in any con-tact strip in both of said planes energizing the said magnetic circuit at the crossover point thereof to establish electrical connection between the last said contact strips.

2. A crossbar switch contact assembly as set forth in claim 1 wherein magnetic remanence in any said energized magnetic circuit maintains said electrical connection 4 after de-energization of the associated operating conductors.

3. A crossbar switch contact assembly as set forth in claim 1 wherein said electrical connection is severed responsive to the energization of one of the operating conductors associated with the energized magnetic circuit in a direction opposite to the said first energization.

4. A crossbar switch contact assembly as set forth in claim 1 wherein the said contact means are electrically connected to the contact strips in one plane.

5. A crossbar switch contact assembly as set forth in claim 1 wherein said contact means includes an insulating member supporting contact elements space separated from the associated contact strips.

6. A crossbar switch contact assembly as set forth in claim 1 wherein each said contact means includes a pair of contact elements and wherein each contact strip of any said magnetic circuit includes one of such pair of contact elements electrically connected thereto.

7. In a crossbar switch contact assembly as set forth in claim 1, support means for normally maintaining an air gap in said magnetic circuit between the associated contact strips and said contact means, the air gap being dimensioned to preclude energization of said magnetic circuit by energization of only one of said contact strips.

8. A crossbar switch contact assembly as set forth in claim 1 wherein de-energ-ization of the operating conductors associated with any energized magnetic circuit opens the said electrical connection.

References Cited in the file of this patent UNITED STATES PATENTS 1,763,284 White June 10, 1930 2,915,607 Levine et al Dec. 1, 1959 2,921,163 Pfleiderer Jan. 12, 1960 2,983,792 Nitsch May 9, 1961 3,002,065 La Tour Sept. 26, 1961 3,009,998 Pfieiderer Nov. 21, 1961 

1. A CROSS BAR SWITCH CONTACT ASSEMBLY COMPRISING A PLURALITY OF FLEXIBLE CONTACT STRIPS OF MAGNETIC MATERIAL ARRANGED IN PARALLEL ROWS IN FIRST AND SECOND PARALLEL PLANES WITH THE CONTACT STRIPS IN ONE PLANE POSITIONED NORMAL TO THE STRIPS IN THE OTHER OF SAID PLANE, CONTACT MEANS POSITIONED BETWEEN THE CONTACT STRIPS OF SAID PLANES AT EACH OF THE CROSSOVER POINTS OF THE CONTACT STRIPS OF ONE PLANE WITH THE CONTACT STRIPS OF THE OTHER PLANE, EACH OF SAID CONTACT MEANS AND ADJACENT PORTIONS OF SAID CONTACT STRIPS DEFINING A SEPARATE MAGNETIC CIRCUIT, AND A SELECTIVELY ENERGIZABLE OPERATING CONDUCTOR EXTENDING LONGITUDINALLY OF EACH OF SAID CONTACT STRIPS FOR GENERATING MAGNETIC FLUX IN THE ASSOCIATED CONTACT STRIP, THE GENERATION OF MAGNETIC FLUX IN ANY CONTACT STRIP IN BOTH OF SAID PLANES ENERGIZING THE SAID MAGNETIC CIRCUIT AT THE CROSSOVER POINT THEREOF TO ESTABLISH ELECTRICAL CONNECTION BETWEEN THE LAST SAID CONTACT STRIPS. 